It is a known fact in all mechanical activity that bolt, nuts etc., that are allowed to be tightened for a period of time, in particular in exposed environments, often can be very difficult to loosen. This depends on that the friction forces between the threads of the nut and the bolt have increased as a result from a number of processes. The most obvious is corrosion, but also time dependent changes of the deformations that arise at the fastening can contribute to an increased friction between the surfaces and thereby an increased resistance against loosening.
One of the most known examples of this problem appears in connection with vehicle wheels. When, for instance, after a puncture, a vehicle wheel has to be dismounted, one has to face the problem to loosen the nuts or bolts holding the wheel at the hub. By security reasons, those nuts and bolts have to be relatively firmly tightened and if they are machine-tightened by so called nutrunner, the method used by garages and rubber workshops, the nuts and bolts are often tightened very firmly. It has been shown that the simple tools normally included in the equipment of the vehicle are not capable to give the torques enabling a person with normal or less body strengths to loosen the nuts or bolts, in particular if they have been tightened for a longer period and "been settled".
In most cases, one has tried to increase the torque to loosen the nuts or bolts. A common method in connection with conventional equipment is to extend the momentum arm by a tube or the like. Despite this, it may be almost impossible for a less strong person to perform the dismounting. It is also common to make a wrench or shock to the dismounting tool to momentarily obtain a larger torque. However, these torques act for very short time periods and such working operations are very tough for the body and lead easily to injuries.
When the nut or bolt at the end loosens, this occurs very rapidly in many cases. The person, which up to this moment has acted on the tool with a large torque, now has to rapidly reduce the torque to parry such a "let go". This may be very difficult to manage and the result is often also here powerful wrenches for nuts, the tool or the person itself.
Most tools are only in contact with the nut or bolt head and this results in that many tools easily slides off the nut and bolt head, respectively, which always involves damages of the head and tool.
A method which is often used for firmly fastened nuts is to apply a torque on the bolt, whereupon the bolt is exposed to heat, gentle strokes and/or chemical solutions. These measures, together with the applied torque, generally makes even the most hard stuck nuts to loosen. This is particularly true if the torque is applied constantly. However, there are no tools intended to help to keep an applied torque, but to achieve a continues torque, this has to be applied by the user.
Another problem that often arises in connection with mounting or dismounting of nuts/bolts is that the space around the nut/bolt is very limited and that the angle strokes for the spanners are limited.
In known art, there are a number of tools which uses ratchet spanner techniques and/or torque amplifying means. However, these principles are always used in a momentarily manner during the use of the tools.
By the Swedish patent application 84.04963-4, such an aid is earlier known. This comprises a circular housing, including a gear switch, the input shaft of which projects from one side of the housing and is there connectable to a crank while its output shaft projects from the opposite side of the housing, presenting a socket gripping around the nut or bolt head. At the housing, a support tube is welded, which by an extension pivotally connected thereto can be brought into contact with the ground or floor base to create a holding-up action during the unscrewing. This tool provides certainly an amplified force by the gearing, but this effect is rather to equal with the effect which is achieved by an extended momentum arm. The torque has to be supplied at all moments. In particular in the proposed embodiment, where the operation is intended to be performed by the motion of a crank, the effect varies substantially depending on the possibilities to apply the necessary torque. Another disadvantage with the known tool is that it is heavy and bulky and has to be adapted in a special manner before it may be used.
Within the known art, there are also other tools enhancing the torque in different ways. The U.S. Pat. No. 4,546,676 discloses a torque amplifying spanner, where when a higher torque is needed, an arm may be displaced giving a higher torque by a gear action. This gives the same effect as extending the momentum arm. Also here, the torque has to be supplied at all moments. Also the German patent DE 29 41 045 discloses a number of torque amplifying hand tools for loosening of nuts. Also here, the idea of an additional handle to achieve this effect is present. This patent document, in one of its embodiments, also presents a solution, where an additional handle acts at the nut by a ratchet spanner principle, whereby this additional handle may be returned if its stroke becomes to large without influencing the nut. This does not change the fact that even in this case, the torque has to be supplied continuously.
The Swiss patent CH 681 606 discloses a double acting ratchet spanner. This ratchet spanner does not use any torque amplification and does not use any kind of holding-up principle, since both shafts are intended to be operated by hand, why the torque also here has to be supplied continuously.